Techniques are known for displaying marks on the outer surface of a side portion that includes a sidewall and a bead portion. The marks are composed of characters, graphics, symbols including barcodes, or the like that indicate a company or brand name, tire size, time of manufacture, or other information. With these techniques, all of the marks have typically been formed by a raised/recessed surface including at least one of a protrusion, a depression, or a ridge.
When marks are thus formed by a raised/recessed surface of the outer surface of the tire side portion, air resistance increases when the tire is rotated with load applied thereon, causing the undeniable problem of a decrease in fuel economy when the vehicle is driven at high speed. Furthermore, the marks are the same color as the ground color of the tire, causing the problem of poor visibility of the marks.
Therefore, a technique has been proposed to print marks on the outer surface of the tire side portion using a printing device such as that disclosed in Patent Literature 1.
In this printing device, a plurality of fixed position upper press rolls, disposed in the circumferential direction of the tire side portion at equivalent angular intervals, press an area between the outside diameter and the printing surface of the tire side portion, and with the tire printing surface being flattened indirectly due to the upper press roles, ink is sprayed from inkjet printer heads while rotating the tire. This printing device can thus print marks of a desired color on the outer surface of the tire side portion. Note that when using this device, it is possible to form not only marks but also decoration by printing on the tire side portion.